samples: replicate nginx image to private ACR

mcr.microsoft.com/azurelinux/base/nginx:1 got updated again on 12/6 and caused test failures on our pipeline
due to the policy annotation of images that depend on nginx getting outdated.

Replicate this image to our private test images ACR so that is stable and doesn't get unknowingly updated or deleted.
We will still test mcr.microsoft.com/azurelinux/base/nginx:1 under "common_images" category and detect
any future possible image breaking changes.

The result of this change will be more stable test results without loosing coverage.

Signed-off-by: Saul Paredes <saulparedes@microsoft.com>

src/agent/samples/policy/yaml/dont-enable-kata-debug/pod-lots-of-layers.yaml

@@ -29,7 +29,7 @@ spec:
         - while true; do echo go; sleep 25; done
     # 6 layers
     - name: nginx
-      image: "mcr.microsoft.com/azurelinux/base/nginx:1.25"
+      image: "marinerconfpodstest.azurecr.io/azurelinux/base/nginx:1.25"
       command:
         - sh
         - "-c"